Doped arylamine-based hole-injection layers (“HILs”) and also hole transport layers (“HTLs”) have been shown to improve the operational stability of organic light-emitting diodes (“OLEDs”). See, for example, Meerheim et al., Applied Physics Letters, 89, 061111-1 to 061111-3 (2006). It is believed that doping may reduce the charge injection barrier between the anode and the HIL and thereby reduce the operating voltage and electric field. Furthermore, the low energy of doped materials may also help in quenching any unwanted excited states forming in the HTL.
A need generally exists to improve synthetic methods for HIL and/or HTL layers which also can lead to improved device processing and performance. Monomer and polymer stability, as well as device stability, can be an important parameter. For example, poly(arylamines) reported by Iida et al., U.S. Patent Application Pub. No. 2007/0207341 and Kido, J. et al. Polym. Adv. Tech., 1995, 7, 31, use exhaustive preparative methods. Furthermore, these monomers can have variable stability under ambient conditions.